Managing Corrosion Of Pipelines That Transport Crude Oils

Special To Pipeline & Gas Journal
March 2013, Vol. 240, No. 3

Oil and gas pipelines play a critical role in delivering the energy resources needed to power communities around the world. In the United States alone, according to the U.S. Department of Transportation (DOT), more than 2.5 million miles of pipelines — enough pipeline to circle the earth approximately 100 times — deliver oil and gas to homes and businesses.

While pipelines are recognized by government agencies such as the DOT and the National Transportation Safety Board (NTSB) as being one of the safest and most efficient means of transporting these commodities, their use still poses an intrinsic risk due to failures and leaks. Although major pipeline failures occur infrequently, several pipeline incidents in recent years have put the issue of pipeline safety into prominent view. In response, both the Canadian National Energy Board (NEB) and the DOT are implementing measures that promote pipeline safety and security.

To better understand how corrosion can impact the safety and reliability of transmission pipelines, NACE International asked several of its members in the oil and gas industry to comment on the challenges faced by the industry when managing corrosion of pipelines, in particular the pipelines that transport crude oils. This report will be presented in two parts with the second article in April.

Panelists are Jenny Been with TransCanada Pipelines; Oliver Moghissi with DNV; Michael Mosher with Alberta Innovates-Technology Futures; Sankara Papavinasam, FNACE,(1) with CanmetMATERIALS; Trevor Place with Enbridge Pipelines; and Sonja Richter with Ohio University. (See their biographies in the sidebar, “Meet the Panelists.”)

NACE: The oil industry is facing concerns by the general public that heavy crude oils, particularly diluted bitumen (dilbit), are corrosive and can lead to leaks and oil spills from transmission pipelines. What are the main challenges the industry faces when managing corrosion of pipelines that transport crude oils?

Moghissi: Internal corrosion is one of many possible threats to a crude oil transmission pipeline that must be managed. It should be noted that crude oil by itself is not corrosive at pipeline conditions, but water can drop out of the crude oil and allow corrosion to occur where it accumulates.

Water carried by heavy crude oils, including dilbit, does not significantly differ in corrosivity from water carried by other crudes. Corrosion in crude oil pipelines is addressed by conventional corrosion control practices and is generally effective. However, pipelines travel over long distances, and what is considered unlikely at one location can become significant when summed over a pipeline infrastructure.
Place: Crude oils, including dilbit, are not corrosive in pipelines. The main technical challenge is that trace water and sediments — not the crude oil — cause corrosion. The presence of crude oil, including the dilbits we have tested, actually decreases the corrosiveness of the standard brine used in standard testing. Although we know that we have a minimally corrosive system, we think it may be possible to reduce corrosion even further — and this possibility is what drives our research and development efforts.